An engine flywheel includes a sensor plate attached to a flywheel cover.
Japanese Patent Application Laid-Open No. 05-312053 discloses an engine crank angle detecting device for detecting a crank angle of an engine by attaching a sensor plate to a side surface of a flywheel and detecting concave/convex portions formed to the sensor plate using a detector disposed in confrontation with the concave/convex portions.
Incidentally, when a flywheel having a coil spring arranged therein as a damper member is used as the flywheel, it is known to have a projecting portion extending inward, which is formed by recessing the surface of a flywheel cover. An end of the coil spring is received by the projecting portion inside of the flywheel cover.
However, when the recessed portion is formed to the surface of the flywheel cover and a sensor plate is attached so as to cover the recessed portion, the sensor plate cannot be attached with the entire attachment surface thereof in intimate contact with the flywheel cover, so that the sensor plate is attached on the recessed portion in a floating state.
Accordingly, when the flywheel cover is deformed while an engine is in operation, the sensor plate cannot be deformed following to the deformation of the flywheel cover. Thus, there is a possibility that stress is concentrated to a welded portion where the sensor plate is fixed in the vicinity of the recessed portion.